How we test dishwashing liquids

Down and dirty with a sink full of dishes

Last updated: 15 January 2019

Whether you wash up dishes regularly or only sporadically and send the bulk of them to a dishwasher, having a dishwashing liquid that works well means less elbow grease from you. Here's how we test them to make sure you only buy the best dishwashing liquids.

Our expert testers

We sent dishwashing liquids from major brands available in supermarkets and smaller companies available online to a laboratory for testing. In-house, we worked out the value for money of each product by measuring how many cleans you'll get from each bottle.

How we choose what we test

Our aim is to test the most popular brands on the market and what you're most likely to see in stores.

We conduct a preliminary check to find what we can buy in store and survey manufacturers to find out about their range of products before putting together a final list that goes to our buyers. They then head out to retailers and purchase each product, or in the case of smaller brands, shop online, just as a normal consumer would. We do this so we can be sure the products are the same as any consumer would find them and not 'tweaked' in any way.

How we test dishwashing liquids

Scrub test

The plates we use in our test are pre-soiled with blends of different types of stains you'll typically have to deal with at home – rice starch, bolognaise and egg yolk.

The stained plates were soaked in a 1% solution of test detergent for 10 minutes before placing the tiles in the scrubbing device. The plates are scrubbed a set number of times with a wet sponge.

Reflectance readings are taken before and after the cleaning process to determine the percentage of soil removed. Each product is tested four times, and the scores are averaged for consistency. The performance score is based on how clean each plate is after reading the result using a spectrophotometer.

Foam test

Using 4mL of each dishwashing liquid in five litres of warm water, we wash pre-soiled plates at timed intervals and count the number of plates cleaned until all the foam in the basin dies.

Why we test this way

We originally started testing dishwashing liquids based on the industry standard which looked at how long their foam lasts, but soon realised that manufacturers were using cleaning agents (called surfactants) that were better at creating foam rather than those that were better at removing grease. This shift was because consumers are under the impression that more foam equates with better performance. But is this really the case?

Rather than counting the bubbles in your washing up water, our current testing emphasises the scrub test scores, as this is will actually show you how well the detergent removes grime from your dishes.

In our most recent dishwashing liquid test, we've included both foaming and scrubbing assessments to give you the full picture. Foam is still important as it helps prevent foodscraps from being redistributed on your plates, but as grime removal is ultimately the best indication of a top-performing product, our overall score gives a far higher weighting to the scrub test (90%).

Sending detergent samples to an external laboratory for chemical analysis is prohibitively expensive, and CHOICE does not have a chemical lab onsite. We test criteria based on a balance of budget and performance, and most members tell us they're more interested in how a dishwashing liquid performs rather than what it is composed of. However, if enough members ask us for detailed chemical analysis we'll forgo another test so we can bring that to you.